Series Question. (1 Viewer)

[chingyloke]

The 20th term of an arithmetic series is 131 and the sum of the 6th to 10th terms inclusive is 235. Find the sum of the first 20 terms.

How would i go about attacking this?

cheers.

 

[lyounamu]

The 20th term of an arithmetic series is 131 and the sum of the 6th to 10th terms inclusive is 235. Find the sum of the first 20 terms.

How would i go about attacking this?

cheers.

20th term = a + 19d = 131 ..(1)

6th to 10th term = (a+5d) + (a+6d) + ... + (a+9d) = 5a + 35d = 235 ...(2)


Solve it simultaneously so you get: 60d = 420 so d = 7
so a = -2

Sum of first 20 terms: n/2(2a + (n-1)d) = 1290

 

[gurmies]

nicely done lyou

 

[bell_9192]

Well lukeman 1st u would stop supporting man utd coz they eat the dick, then start supporting liverpool coz they make manure eat the dick, and finally u should ask folksey and bring urself down to our level....normality lol

 

[random-1005]

The 20th term of an arithmetic series is 131 and the sum of the 6th to 10th terms inclusive is 235. Find the sum of the first 20 terms.

How would i go about attacking this?

cheers.

a person that does 4 unit is asking about a really easy 2 unit question, how does that work?

 

[L]

u should ask harry potter

he is a real magician